I thought I read somewhere that the two practice test attempts are administered strangely. As such you take the first practice test, then the second test is made up of missed questions fro the first test. Is this correct?

I've only ever used 1 practice exam, so I'm not too sure about that. That might be possible. I will say that the practice exam was very similar to the actual test - was a little bit tougher, but most of the concepts/questions asked were close to the same. So in taking your practice test(s), if you score above a 90 you probably won't have a problem passing the actual exam.